Color television



1953 H. G. LUBSZYNSKI ET AL 2,66

COLOR TELEVISION Filed Dec. 15, 1947 /nven7brs: HANS GERHARD LUBSZYNSKI'REGINALD SIDNEY WEBLEY W 64m ,4 for/19y 93 lea COLOP TELEVISION HansGerhard Lubszynski, N orthwootl, and Reginald Sidney Webley, Hayes,England, assignors to Electric & Musical Industries Limited, Hayes,England, a company of Great Britain Application December 13, 1947,serial No. 791,542

12 Claims,

This invention relates to electron discharge apparatus for generatingsignals suitable for use in colour television.

Various proposals have heretofore been made 2 colour mixed with saidfirst colour, and signal generating means which is arranged to utilisesaid groups of electrons so as to generate one set of picture signalsrepresentative of compofor generating colour television signals, butmost 5 nents of said iinage of said first colour and a of these priorproposals have relied upon the use second set of picturesignalsrepresentative of of colour filters through which an image of ancomponents of said image of said second colour. object for transmissionis projected onto a suit- The apparatus employed in the invention mayable screen from which picture signals can be decomprise an electrondischarge device following rived. The use of colour filters forgenerating m the same general construction as has been propicturesignals for colour television purposes is posedfor generatingmonochromatic picture sigundesirable from many points of View and thenals, the apparatus, however, being modified by object of the presentinvention i to provide an the provision of said electron separatingmeans. improved apparatus for generating picture sig- Preferably, thegroup of electrons is caused to nals for colour television in which theuse of (201- impinge on a target electrode of the charge-storour filtersfor generating signals is avoided. age type, the target electrode beingscanned by When a light image of mixed colour is proa cathode ray beamso as to restore the elements jected onto a photo-electric cathode,photo-elecof the target electrode to datum potentials, the trons arereleased from the cathode and the vearrangement being such that theimage is 'ultilocity of the electrons so released depends on the niatelyeffectively separated into sets of picture colour of the elemental areasof the image illusignals representative of the primary colour(361.cminating the photo-electric cathode. Thus, if ponents of theimage. one elemental area of the photo-electric cathode In order thatthe said invention may be clearly is illuminated with blue light thenthe maximum understood and readily carried into effect, the emissionenergy of the photo-electrons released 5 same will now be more fullydescribed with refiroin thi elemental area will be greater than thecrease to the drawings, in which maximum emission energy ofphoto-electrons re Figure 1 illustrates diagrammatically an elecleesedfrom another elemental area of the phototron'discharge' device suitablefor use in the inelectric cathode which is being illuminated forvention, example with green light, and a substantial irac- Figure 2 is ablock diagram of a television tion of the electrons released by the bluelight transmitter operating in accordance with one will have emissionenergies exceeding the maxlembodiment of the invention,

emission energy of the electrons released Figure 8 is a diagrammaticView of a modifiby the green light. Similarly the maximum emiscation ofthe discharge device shown in Figure 1, energy of the electron releasedby the green 5 Figure 4 is a diagram illustrating a diiierent light willbe greater than the maximum emission manner of operating the deviceshown in Fig energy of photo-electrons released from an eleure '1,mental area of the photo electric cathode which Figure 5 illustratesdiagrammatically a Inc-db is being illuminated by red light andsubstantial ficationof the device hawn in Figure 1 for usg fraction ofthe electrons released by green light 40 with the manner of. operationshown in Figure 4, will have emission energies exceeding the max- Figure6 illustrates diagrammaticmly a further I ssion energy of electronsreleased by red embodiment of the invention, and

t. present invention i based on the Figure 7 illustrates a modificationof the arpnnoiple of utilising the difference of emission rangementshown in Figure 6. energies of electrons released by light of difierentThe present invention is based on the phenomcolours in order to gener tpicture signals for enon that when a light image of mixed colours iscolour television. projected onto a photo-electric cathode the emis Thepresgnt ti n rovides apparatus for sion energies of the electronsreleased from the generating picture signals for colour televisionhoto-electric cathode depends on the colour of wherein means re providedfor utilising the the incident light. By setting up a suitable fielddifieren c in energy between electrons released it is possible toexercise a control on the released y light of one colour compared withlight of electrons which is dependent upon their emission another colourto generate picture signals repreenergies and thereby separate releasedelec rons sentative of different colour components of an into groupsaccording to the emission energies of image, the electrons and henceaccording to the colour m aratus for carrying the invention into ofincident light. For example, the controlmay eiiect may comprise meansfor separating eleobe effective to produce one group containing electrons released by a light image of mixed colours trons released by lightof a first colour, another into one group containing electron releasedby group containing electrons released by light of light (me 1 and intoa second group cona second colour mixed with said firstcolour and tamingelectrons released by light of a second a third group containingelectrons releasedby light of a third colour mixed with said first andsecond colours, the first group of electrons can then be employed toobtain a set of picture signals corresponding to said first colour, thefirst and second groups can be employed to obtain a set of picturesignals corresponding predominantly to said second colour bysubstantially balancing out said first colour, and similarly the secondand third groups can be employed to obtain a set of picture signalscorresponding predominantly to said third colour. The control may forexample be exercised by applying potentials to a control electrodedisposed adjacent to a photo-electric cathode such that effectively onlyelectrons released with energies exceeding a predetermined value arepermitted to pass said electrode. Figure 1 of the drawings illlustratesan electron discharge device suitable for use in one form of theinvention and which, when used in conjunction with the circuit shown inblock form in Figure 2, enables television signals to be obtained whichare representative of the three primary colours of a coloured image.

Figure 1 illustrates an electron discharge device which constitutes apick-up tube similar to a device known as an image orthicon. Thedischarge device shown comprises an evacuated envelope I having at oneend a photo-electric cathode 2 onto which a light image of mixed colourscan be projected cal system indicated at d. On projecting an opticalimage onto the photo-electric cathode 2 photo-electrons are releasedwhich are projected and focussed onto a charge-storage target electrode5. Adjacent to the cathode 2 is disposed a control electrode t in theform of a grid which, in operation, is biasscd in such a way as toallow, first, only electrons liberated from the oathode 2 by blue lightwith energies exceeding the maximum emission of by green light, thenelectrons liberated by blue light mixed with green light with energiesexceeding the maximum emission energy of electrons released by red lightand finally all the electrons liberated by blue light mixed with greenand red light to be transmitted through the interstices of the electrode6 and caused to impinge on the target 5. It will be convenient to referto electrons liberated with energies exceeding the maximum emissionenergy of electrons released by green light as blue electrons, to referto electrons liberated with energies not exceeding the latter maximumbut exceeding the maximum emission energy of electrons released by redlight as green electrons, and to refer to electrons liberated withenergies not exceeding the last-mentioned maximum as red electrons. Itwill of course be appreciated that a number of the green electrons mayin fact be liberated by blue light, while a number of the red electronsmay in fact be liberated by blue and green light, but these should notprevent satisfactory operation of the apparatus. The target is of theso-called double-sided type and on the side of the target 5 facing thecathode 2 is a collector electrode 1 in the form of a grid forcollecting secondary electrons released from the target 5 whilst on theside of the target 5 remote from the photo-electric cathode "2 is anelectron gun indicated conventionally at 8 which serves to generate abeam of electrons for scanning the target 5, scanning of the target 5 bythe beam of the gun 8 serving in known manner to restore the elements ofthe target 5 to an equilibrium potential, electrons which are notemployed for through a suitable optienergy of electrons released drestoring the elements being returned to multiplying electrodesindicated at 6 which serve in known manner effectively to multiply thereturned electrons, the final electron stream serving to develop picturesignals. The discharge device shown in Figure 1 is arranged within acoil It: which serves to set up a substantial axially symmetricalmagnetic field which is necessary for the operation of discharge devicesof the kind shown in Figure l. A pair of coils H is provided between thecathode 2 and the target 5, these coils having applied thereto, inoperation, a rectangular pulse Waveform in such a manner that thephoto-electrons released from the cathode 2 are caused to be projectedalternately onto the upper and lower portions of the target 5, asindicated by the dotted lines, the photo-electrons being projected on toeach portion for the duration of a colour frame. The electron beam fromthe gun 8 is arranged to scan the electron images applied to the target5 in such a phase that during one colour frame the beam always scansthat portion of the target which has been charged by photo-electronsduring the previous colour frame. The electron image from the cathode 2is focussed by the coil is and is accelerated onto the target electrode5 by a cylindricai anode i2 applied to the wall of the tube l. Theelectron beam from the gun 3 is also focussed by the coil it! whiledeflecting coils, some of which are shown at it impart the line andframe scanning deflections to said beam from the gun 8, the electronsfrom the gun 3 being accelerated by a cylindrical anode 54 applied tothe wall of the tube i, as shown.

The control electrode 6 as aforesaid is arranged to be biased by meansof potential pulses in such a manner that first blue electrons arereleased for a predetermined interval equal to the duration of a colourframe, these blue electrons being projected say onto the upper portionof the target 5 and the charges produced by said electrons being storedby the target 5. Then the Potential applied to control electrode 6 ischanged so that it allows blue and green electrons to be released, theelectron image resulting from these blue and green electrons beingprojected onto the lower portion of the target 5 for an interval ofequal duration and during the projection of blue and green electronsonto the target 5 the upper portion of the target is scanned by the beamemanating from the gun 8. Then the potential applied to the controlelectrode 6 is again changed so that it allows blue, green and redelectrons to be released, these electrons being projected onto the upperportion of the target 5 during which period the lower portion of thetarget is scanned by the beam of the gun 8 and so on, so that the outputof the tube derived from the multiplying electrodes 9 consists of threesets of signals. The first set of signals is generated during one colourframe and is representative of the blue component of the image, the nextset of signals is generated during the next colour frame and isrepresentative of the blue and green components of the image, whilst thethird set of signals, which is generated during the following colourframe is representative of the blue, green and red components of theimage, the said sets being generated in the same sequence duringsuccessive colour frames.

Referring now to Figure 2 of the drawings, the signal output from thedevice shown in Fig 1 is amplified by an amplifier i5 and the three setsof signals aforesaid are passed to a switching device it, theconstruction of which is such that the signals are passed in accordancewith the.

phasing of the intervals in which they are generated to a transmitter llor to a storage device it? iii, or to a combination of them.

The devices 58 and is may each comprise for example an electrondischarge device having a target electrode which can store charges andwhich can be scanned on one side with a high velocity beam of electronsand on the other side with a low velocity beam of electrons. If withthis arrangement, the first set of picture signals caused to modulatethe high velocity beam of electrons in the device it during one colourframe, a positive charge image is produced on the storage electroderepresentative of said set of signals, and during the subsequent colourframe the signals are reproduced. by scanning with the low velocity beamof electrons so as to discharge the storage electrode, a signal platebeing provided capacitatively with the storage electrode from which thereproduced signals are derived. The reproduced signals can then becombined on opposite phase with the second set of signals in a suitableamplifier the resultant of the combined signals being signals which arerepresentative effectively only of the green electrons, the second setof signals being simultaneously caused to modulate the high velocitybeam of electrons in the device it so that after storage they cansubsequently be combined in opposite phase with the third set ofsignals, so as to produce signals representative effectively only of redelectrons. Alternatively the storage devices it and It may each comprisean electron discharge device having a charge storage electrode providedat one side with a signal plate capacitatively associated with thestorage electrode and at the other side with a control electrode in theform of a grid or grill which means being provided for scanning thestorage electrode with an unmodulated beam of electrons from the side atwhich the grid is located. If, with this arrangement, the first set ofsignals is applied to the signal plate of the device It durone colourframe while the storage electrode is being scanned by said beam ofelectrons, a charge image will be produced in said storage electroderepresentative of said first set of signals. During the subsequentcolour frame, the second set of signals can then be applied to thesignal plate while the storage electrode is being again scanned by thebeam of electrons, and a is maintained at a uniform potential,

resultant signal derived from thesignal plate which is representative ofthe difierence of the two sets of signals, and therefore representativepredominantly of the green component of the original image. The secondand third sets of can similarly be combined in appropriate phase withthe aid of the other storage device i9 whereby signals are obtained fromthe latter device which are representative predominantly of the redcomponent of the original image.

The sequence ofoperation of the switching device it may be as follows:the first set of signals is caused by the device it to be fed to thetransmitter ll during said first colour frame, said set of signals beingsimultaneously fed to the storage device it. The second set of signalsis then fed during said second colour frame by the device it to thestorage device It and also to the storage device It whilst the output ofthe device is is fed to the transmitter H. The output signals from thedevice [8 will then be representative-of the green component oftheoriginal image.

unmixed with the blue component. Then the third set of signals is fedduring said third colour frame to the storage device E9, the outputsignals of this device then consisting only of the red components of theoriginal image. At the same time the storage device I 8 is conditionedto receive the first set of signals of another colour frame bydischarging the elements of the storage electrode. Similarly, during thenext colour frame the storage device I 9 is conditioned for commencingthe next cycle. Since the first set of signals, which are representativeof the blue component of the image, is fed directly to the transmitterll, whilst the signals representative of the green and red components ofthe original image are derived from the storage devices It and It, itwill of course be necessary to employ suitable amplifying or attenuatingmeans in the channels feeding the transmitter l7 and the devices ft andis so that the respective signal amplitudes are effectively proportionalto the original signals derived from the device shown in Fig. 1. Theseamplifying or attenuating means can also be used to correct if requiredthe colour response of the photo-electric cathode 2. It is possible thatimperfect signals will be derived from the devices It and it when amoving object is projected onto the cathode 2, but since the framefrequency for a colour television transmission will necessarily beincreased compared with a monochromatic system, these imperfect signalsmay not be a serious disadvantage.

The type of discharge device shown in Figure 1 is usually operated withcathode potential stabilisation; that is to say, the target 5 isdischarged with a low velocity beam of electrons from the gun 8. Withthis mode of operation, it is necessary to set up positive charge imageson the target 5. The photo-electrons from the photo-electric cathode 2are therefore projected on the target 5 with sufiicient velocity torelease secondary electrons, these secondary electrons being absorbed bythe electrode 5.

The invention is however, not limited in its use to the general type ofdischarge device shown in Figure 1 since the invention can also beemployed with other kinds of devices. For example it may be applied todischarge devices wherein the electron image from the photo-cathode 2 isprojected with a low velocity on the target 5 so as to charge theelemental areas of the storage electrode to negative potentials independence upon the intensity of the projected electron image, i. e. soas to form a negative charge image on the target 5,

r and wherein a control electrode in the form of a mesh is disposedimmediately in front of the scanned side of the target 5. Potentialdifferences are thus set up between the elemental areas of the target 5and the control electrode in dependence upon said negative charge image,the control electrode being maintained at a constant potential. Oneproposed form of device of this kind is described in United Statespatent application Serial No. 792,576, and according thereto the target5 is scanned by means of a beam of electrons of sufiicient velocity torelease secondary electrons from the target 'i.

released from the target 5 escape through the control electrode and areutilised for generating electrical signals by directing them to anelectron multiplier, the number of electrons which escape from eachelemental area being dependent upon the potential difierenceestablished, as aforesaid, between the respective elemental area and thecontrol electrode. In another form of device of The electrons this kind,the target is rendered photo-sensitive on the scanned side thereof,scanning being effected by means of a light spot projected, for example,from the fluorescent screen of a cathode ray tube. The light spotreleases electrons from the target 5, the release being controlled asaforesaid by the control electrode. If either form of device of thiskind is employed, the grid 6, instead of being disposed adjacent to thecathode 2, may alternatively be disposed as shown in Fi ure 3 adjacentto the target 5 since the photoelectrons have a low velocity in thevicinity of the target 5. In this case, the photo-electrons releasedfrom the cathode 2 are accelerated by a grid 2?.- and pass through thegrid 6 before impinging on the target 5 so as to charge it negatively.By applying suitable potential pulses to the control electrode 6, thetarget 5 can be charged respectively by blue electrons, blue and greenelectrons, and blue, green and red electrons.

Instead of deriving signals representative of the three primary coloursof the image by the use of the devices i8 and 19 it is possible toobtain signals representative of said primary colours from the aforesaidblue, blue and green, and blue, green and red electrons by causing saidelectrons to impinge on the target 5 with such energies that theprimary/secondary electron emission ratio is varied according towhichever of the three sets of electrons is being projected. Forexample, the blue electrons released from the photo-electric cathode 2of Figure 1 can be caused to impinge on the target 5 with such energythat they release more than one secondary electron for each primaryelectron. The blue and green electrons can be caused to impinge on thetarget electrode with low energies so that they release substantially nosecondary electrons and if the image of the blue and green electrons issuperimposed on the target which has been charged by the blue electrons,then the charges due to the blue electrons will eifectively cancel oneanother so that a charge image will result corresponding efiectivelyonly to green electrons. Similarly a charge image can be ultimatelyobtained which is representative only of red electrons. The change inenergy of the electrons in order to cause the primary/secondary electronemission ratio to vary may be effected by applying suitable rectangularpotential pulses to the photo-electric cathode 2 and the grid 6 ofFigure 1 thus effectively varying the potential of the source ofelectrons. The sense of the pulses may be arranged so that the chargeimages resulting from the mutual cancellation are either positive ornegative according to the type of electron discharge device employed.

The sequence of operations when operating the device shown in Figure lin this manner is represented in Figure 4 from which it will be observedthat, firstly, as shown at a, a blue electron image is focussed onto theupper portion of the target 5 for the duration of half a colour frame soas to form on said target electrode a positive charge image. Theelectron image is then completely cut off for the remainder of the frameinterval, for example, by applying a strong negative bias to the grid 6as represented at b. Then a blue electron image is focussed onto thelower portion of the target 5 for the duration of half a colour frame,so as to form on the lower portion of said target electrode a negativecharge image as represented at 0. Then an image resulting from blue andgreen electrons is superimposed on the negative blue image for theduration of the remaining half of the colour frame so as to form apositive charge image, the charges resulting from the blue componentseffectively cancelling and leaving a charge image corresponding only togreen electrons. This step is shown at d. Then blue and green electronsare focussed onto the upper portion of the target for the duration ofhalf the n xt colour frame so as to form a negative charge image of blueand green electrons, as shown at e. Then a charge image of blue, greenand red electrons is superimposed on the negative charge image formed byblue and green electrons for the duration of the remaining half of thelast-mentioned colour frame so as to form a positive charge image sothat the ultimate charge image set up on the screen 5 is a charge imageresulting only from red electrons, as shown at f. The scanning of thecathode ray beam from the gun 8 is so phased that the beam always scansthe charge image stored during the previous colour frame. Thus, duringthe sequences 0 and d the beam is caused to scan the portion of thetarget upon which the blue image is formed at a in Figure 4 and duringthe sequences e and f the beam is caused to scan the green image at d inFigure 4 and so on. If any this-matching of colour occurs due toincorrect secondary emission factors it may be possible to compensatefor such nus-matching by varying the ratio of the exposure time of thecharge images. Colour fringes resulting from fast-moving objects couldbe transformed into slightly blurred edges of the correct colour byalternately projecting the images onto the target electrode at a highfrequency instead" of projecting them separately each for a duration ofhalf a colour field.

In addition, the apparatus illustrated can be operated in such way thatinterlaced scanning is efiected. In that case, each complete scanningraster traced by the beam on the target 5 is effected in two frames orsequences of lines one of which i traced on the lower portion of thetarget 5 and the other of which is traced on the upper portion of thetarget 5. By displacing the upper charge image relatively to the lowercharge image on the target 5, or vice versa, in the vertical directicnby half the vertical displacement which the scanning beam undergoesduring a line period, it is arranged that the lines traced on the chargeimage on the lower portion of the target 5 interlace With the linestraced on that on the upper portion of the target 5. Alternatively, the

- same result can be achieved by relatively displacing the two sequencesof lines which are traced respectively on the upper and lower portionsof the target 5. lhe lines of each sequence are spaced apart to allowthe lines of the other sequence to interlace therewith and, in order toremove the charges stored in the gaps between the lines of eachsequence, the scanning beam can be caused to discharge these gaps duringthe return times between successive lines. Since the return times areappreciably shorter than the line times, the beam current may beincreased during the return times to assist in discharging the gaps, forexample by applying positive potential pulses to the modulatingelectrode of the gun 8. Simultaneously, the signal output may besuppressed in the amplifier or in the electron multiplier during theline return times. The d scharge of the gaps can also be assisted bysllghtly defocussing the beam during the line return times andsimultaneously superimposing rectangular pulses of line frequency on thevertical scanning waveform so that the beam, during the line returntimes, is shifted slightly backwards in the vertical direction.

Instead of applying pulses to the cathode 2 and grid as aforesaid, thechangeover required to afford the positive and negative charge imagesmay be eiiected by means of a grid 2|, as shown in Figure 5, this gridbeing arranged in front of Figure ,6 of the drawings illustrates a,further embodiment of the invention. As shown in this figure there isdisposed at the end of the onred electrons.

Assuming that the maximum emission energies of red, green and blueelectrons are a, b and c electron volts respectively, where a is smallerthan I: and b is smaller than c, then the potential applied to theelectrode 22 is maintained in sequence for each colour field at -cvolts, b volts and u volts respectively, and the potential of theelectrode 2d is maintained in similar sequence at -29 volts, a volts andZero Volts. When the potential of the elec trode 22 is -c volts and thepotential of the elec trode 24 is volts, cannot collect any or thereleased electrons so that the released electrons pass through the gridit, and red and green electrons are then repelled by the electrode 28and caused to return to the electrode 23, blue electrons being howeverpermitted to pass through the interstices of the electrode 2 3 to thetarget 5. When the potential of the electrode 22 is -29 volts, and thepotential of the electrode 2d is a 5' volts, blue electrons arecollected by the electrode 22 while red and green electrons pass throughthe electrode 23, red electrons being finally reflected to the electrodeby the electrode while the green electrons to the target 5. When thepotential of the electrode 22 is -a volts and the potential of theelectrode 24 is zero volts, then blue and green electrons are collectedby the electrode 22 and only red electrons pass through the electrode 23and no electrons are reflected to the electrode 23 by the electrode 2 inthis way, red, green and blue electron images are formed in sequence onthe target electrode 5. By applying suitable poten tial pulses to thedeflecting coils H in timed relationship with the change of potentialson the electrodes 22 and 2d, a red image can be formed on the lowerportion of the target then a green image on the middle portion of thetarget 5 and then a blue image on the upper portion of the target 5. Thered image is arranged to be scanned by the beam from the gun 8 whilstthe green image is being applied to the middle portion of the target,and so on.

If desired, the grid electrodes 23 and E l may be combined as .sho n inFigure 7. For example, a mesh 25 of aluminium may be provided which isinsulated by the provision of an anodised layer the right-hand side ofthe mesh 25, as shown in Figure '7, being suitably lapped that it is notcovered by the layer fit and on the left-hand side of the mesh 25 thereis provided a sputtered or evaporated metal layer 2? which replaces theelectrode Whilst the right-hand side of the mesh is provided with aphoto-electric layer which replaces the electrode The electrodes 2? andare thus shown facing the 013-- n it direction from that in Figure 6.

hough the invention has been described as applied to several kinds ofelectron discharge deit will be understood that the invention is notlimited in its use to electron discharge devices oi the kinds describedas it can be applied to any suitable device such as has been proposedfor generating television signals, such as the socalled image dissectcrsor electron discharge devices in which the optical image projected ontoa target electrode is converted into an electron stream by scanning aphoto-electric cathode with a light spot so as to derive from thephoto-elem trio cathode a beam of electrons which scans said targe Weclaim:

1. In apparatus for generating picture signals for colour television, anelectron discharge pickup tube having a photo-electrically sensitivesurface arranged for exposure to light images of mixed colours, meansfor establishing a potential field for differentially controlling theelectrons released by a light image from said photosensitive surface independence upon the energies of said electrons, and means for generatingfrom said differentially controlled electrons picture signalsrepresentative of diiferent colour components of a light image.

2. In apparatus for generating picture signals for colour television, anelectron discharge pickup tube having a photo-electrically sensitivesurface arranged for exposure to light images of mixed colours, meansfor separating electrons re leased by a light image from saidphoto-electrically sensitive surface, in dependence upon their energies,into one group containing electrons released with emission energiesexceeding one level and a second group containing electrons r and meansI01 generating from said groups of electrons one set of picture signalsrepresentative of components of said light image of a first colour and asecond set of picture signals representative of components of said lightimage of a second colour.

In apparatus for generating picture signals for colour televisionaccording to claim 2, said tube having means for generating one set ofpicture signals from said first group of electrons, means for generatingfurther signals from said second group of electrons, and means forcombining said further signals with said first set of picture signals inphase opposition to generate thereby said second set of signals.

4. In apparatus for generating picture signals for colour televisionaccording to claim 2, said tube having a charge storage electrode, meansfor causing said groups of electrons to produce superimposed chargeimages of opposing polarity on said charge storage electrode toeffectively balance out charges representative of electrons havingemission energies exceeding said first level components from theresultant charge image, and means for generating picture signals fromthe re sultant charge image to generate thereby said second set ofpicture signals.

5. In apparatus for generating picture signals for colour television, anelectron discharge pickup tube comprising a photo-electrically sensitivesurface arranged for exposure to light images of mixed colours, meansfor separating electrons released by a light image from saidphoto-e1ectri cally sensitive surface, in dependence upon theirenergies, into one group containing electrons released with emissionenergies exceeding one level and a second group containing electronsreleased with emission energies exceeding another and lower level butnot exceeding said first level, means for generating one set of picturesignals representative of components of said light image of a firstcolour from said first group of electrons and for generating a secondset of picture signals representative of said light image of a secondcolour from said second group of electrons.

6. In apparatus according to claim 5, said electron separating meanscomprising a first control electrode, means for applying one potentialto said control electrode during intervals to repel all electronsreleased with emission energies exceeding said lower level and forapplying a different potential to said control electrode at otherintervals to collect electrons with emission energies exceeding saidfirst level and to repel electrons with lower emission energies, asecond control electrode arranged in the path of electrons repelled bysaid first control electrode and means for applying potentials to saidcontrol electrode to allow only the passage of electrons with emissionenergies exceeding said first level at said first intervals and to allowthe passage of all elec trons with emission energies exceeding saidlower level at said other intervals.

'7. In apparatus for generating picture signals for colour television,an electron discharge pickup tube having a photo-electrically sensitivesurface arranged for exposure to light images of mixed colours, meansdependent upon the energies of the electrons released from said surfacefor separating the released electrons alternately into one groupcontaining electrons released with predetermined energies and a secondgroup con.- taining electrons released'with different energies, a chargestorage electrode, means for directing said groups of electronsalternately to different portions of said charge storage electrode tomduce charge images alternately on said portions, means for causing abeam of electrons to scan said portions of the charge storage electrodealternately in reverse order from that in which said charge images areproduced in said portions, and means for deriving picture signalsrepresent ative of different colour components of a light image from thescanning of said charge storage electrode.

8. In apparatus for generating picture signals for colour television, anelectron discharge pickup tube having a photo-electrically sensitivesurface arranged for exposure to a light image of mixed colours,potential-operated meansfor differentially controlling electronsreleased by a light image from said surface in dependence upon theenergies of said electrons, means for applying potentials to saidpotential-operated means to separate electrons released from saidsurface alternately into one group containing electrons of predeterminedenergies and into a second group containing electrons of diiierent 12energies, andmeans for sequentially generating from said groups ofelectrons one set of picture signals representative of a first colourcomponent of a light image and a second set of picture signalsrepresentative of a different colour component of the light image.

9. In apparatus for generating picture signals for colour televisionaccording to claim 8, said potential-operated means comprising a controlelectrode pervious to electrons and arranged in the path of electronsreleased from said photoelectrically sensitive surface. 10. 111a'paratus for generating picture signals for color television, anlectron discharge pick-up tube comprising aphoto-electrically sensitizedsurfacearranged for exposure to a light image oi mixed-colorsfnieans forcontrolling the path m. the m t ress released from said surface by alight imageind'ependence upon the energiesof the released electrons, andmeans for generating from the controlled electrons picture signalsrepresentative of difierent color components of a lightimage to whichsaid surface is exposed.

ll. In apparatus for generating picture signals for eolontelevision, anelectron discharge picliup tube having a photo-electrically sensitivesurfacearranged'for exposure to light images of mixed colors, means forseparating electrons released'lfro'm'said surface by a light image independence upon the energies of said electrons into groups containingelectrons with energies in different energy ranges, and means forgenerating picture signals representative of different color componentsof the light image from said groups of electrons.

' 12. In apparatus for generating picture signals for color television,an electron discharge pickup tube comprising a photo-electricallysensitive surface arranged for exposure to light images of mixedcolors,electrode means effective in the path of electrons released by a lightimage from said surface, means for applying potentials to said electrodemeans during one set of periodic intervals to separate electrons withemission err-- ergies'in one energy range from electrons re leased by alight image from said surface, means for applying different potentialsto said electrode means during another set of intervals inter calatedwith said first set to separate electrons with emission energies in. adifferent energy range from electrons released by a light image fromsaid surface, and means for generating pic ture signals representativeof different color components of said light image from the electron:

' separated during said different sets of intervals.

HANS GERHARD LUBSZYNSKI. REGINALD SIDNEY WEBLEY.

References Cited in the file of this patent UNITED STATES PATENTS

